View More Details in Data Center
Provide Feedback

Percent of Land Coverage Within Land Capability Class 1b (allow up to 1% impervious coverage)

Lands classified as 1b are among the most sensitive in the Tahoe Region and can support the least amount of land disturbance. The percent of land coverage within land capability class 1b indicator measures the percent of land coverage on class 1b lands in the Tahoe Region. The indicator allows up to one percent impervious coverage within land capability class 1b. Land capability class 1b is environmentally sensitive land and includes low-lying stream environment zones (SEZ), stream channels, marshes, floodplains, meadows, and other areas with surface or groundwater. class 1b lands are critical for natural water filtration, storage, and conveyance of surface runoff. Encroachment on these areas reduces their potential to filter sediment and nutrients and the amount of surface runoff they can effectively treat. Naturally functioning SEZs also provide open space, flood flow capacity, riparian vegetation, fish and wildlife habitat, and buffer urban uses in developed areas. Since the adoption of the 1987 Regional Plan, new coverage or even temporary disturbance in class 1b has been prohibited. The updated 2012 Regional Plan carried forward all protection for class 1b (SEZ) lands. 

Status

Percent cover in each Bailey land capability class relative to the allowable coverage in class.

Data was created by Tahoe Regional Planning Agency. Access detailed datasets on Tahoe Open Data, including, bailey land capability feature class, remotely sensed impervious coverage feature class, and the permitted coverage summary.

Evaluation Map

Land capability Class 1b lands and impervious surfaces within the Tahoe Region.

2023 Evaluation

Status
Considerably Worse Than Target
Trend
Little or No Change
Confidence
Moderate
View Evaluation

Applicable Standard

SC2: Impervious cover shall comply with the "Land Capability Classification of the Lake Tahoe Basin, California-Nevada, A Guide for Planning", Bailey, 1974. Allowable percent of impervious cover in Land Capability subclass 1b - 1%.

Key Points

  • Between 2020-2023, 1.6 acres of impervious coverage was removed from class 1b lands.

  • The Regional Plan prohibits further disturbance of class 1b land, but progress toward attainment of the impervious cover standard for class 1b remains challenging. Attainment would require the removal and/or relocation of 682 acres of impervious cover, roughly 86 percent of all existing impervious cover in class 1b portions the Region. It would also likely require the removal and buyout of large portions of existing private development. Removal or relocation of this magnitude may be infeasible in a reasonable timeframe.

  • The TRPA Code of Ordinances restricts new land coverage or permanent disturbances in sensitive areas, specifically in classes 1a, 1b, 1c, 2, and 3, with only a few exceptions allowed.

  • The outlook for the Region’s SEZs is significantly brighter today than when the standard was adopted. Development forecasts when the standard was adopted predicted further SEZ loss, between 1,550 and 1,770 additional acres by 1995, without regulation. That did not occur. The USDA Forest Service and the California Tahoe Conservancy acquired and protected over 900 acres of SEZ, and permit conditions and development restrictions prevent any new degradation of non-protected SEZs.

  • To date, projects have restored 1,057 acres of SEZ. Accounting totals historically omitted USDA Forest Service projects completed in the 1980s. When 680 acres of SEZ restoration completed by the Forest Service between 1984 to 1987 is added, partners have restored 1,604 acres of SEZ and restored/acquired nearly 2,500 acres.

About the Threshold

This indicator measures the percent of land coverage on different land capability classes as described by Bailey (Bailey, 1974) and updated with the most recent soil survey by the Natural Resources Conservation Service (NRCS) in 2007 (Loftis, 2007; USDA-NRCS, 2007). Impervious cover is a primary indicator of land disturbance. Excessive impervious surface within a watershed contributes to sediment and nutrient inputs to Lake Tahoe and its tributaries impairing water quality, altering surface hydrology and groundwater recharge regimes. The results are often negative impacts on soil health, fisheries, wildlife habitat, and vegetation growth. Impervious surfaces include hard coverage such as roads, buildings, driveways, and parking lots, and soft coverage with soil compaction as a result of use, but where no structure is in place.
Impervious cover is created through use or development on natural lands. This could be for commercial, residential, recreational, and other activities, and encompasses the spectrum of human uses that involve physical modification of the environment. The economy plays a large role in the housing market and the business environment, which are both among the most important drivers of new land coverage in the basin.

Delivering and Measuring Success

EIP Action Priorities

EIP Indicators

  • Impervious Coverage Retired

    Between 2020 and 2023, EIP partners retired (i.e., permanently remove from future use) 36,416 square feet (0.84 acres) of Class 1b coverage.

Example EIP Projects

Rationale Details

Considerably Worse Than Target. Land capability Class 1b has 797 acres of existing acres of impervious coverage, 683 acres more than are allowed under the Bailey 1b threshold standard of 114 acres. This makes it "considerably worse than target."

All permitted projects that add coverage pay a water quality mitigation fee. There were 720 projects that paid water quality mitigation fees between 2000 and 2023, with more than $2.37 million collected during the period for the creation of 1.275 million square feet of added coverage (29 acres) in all classes. During the period, more than 232,000 square feet of coverage (5.3 acres) was removed on 45 parcels as a requirement of permit conditions and from Environmental Improvement Program projects to remove and retire coverage.
Little or No Change. The trends for Impervious cover within class 1b was determined to be "little or no change". Between the 2019 Threshold Evaluation and the 2023 Threshold Evaluation, impervious coverage in class 1b was reduced by 1.6 acres, or -0.2 percent.

Confidence Details

Moderate. For the 2023 analysis, TRPA used the 2019 baseline and added or removed coverage based on the cumulative accounting of acres of cover added in each land capability class based on the rigorous tracking from TRPA permitting data and Environmental Improvement Program tracking. All permitted projects that add coverage pay a water quality mitigation fee; these fee collections were used to assess added coverage. Some inaccuracy is introduced due to unpermitted impervious cover that may have been added or created in the Region, for which no permit was acquired. This reduces the status confidence to moderate. The 2019 Threshold Evaluation for impervious coverage was based on an updated analysis of high-resolution aerial imagery and hand digitizing features from multispectral images collected in 2018 and 2019.
Moderate. Because of the change in source data to using permitting mitigation fees for the 2023 evaluation, comparison of the trend is rated as moderate confidence.
Moderate. There is “moderate” overall confidence based on the accuracy of the impervious surface data and the land capability class results.

Additional Figures and Resources

No photos available.

Coverage Changes 2020-2023
Uploaded On
10/18/2024
File Type
PDF
Description
This table provides the detailed accounting of coverage added by parcel between 2020-2023, based on TRPA permitting actions and the payment of water quality mitigation fees. The table also includes coverage removed and retired through permitting as well as coverage removed by Environmental Improvement Program projects. The coverage changes are reported by year and land capability class.